Date: January 1739

"Since the imagination, therefore, in running from low to high, finds an opposition in its internal qualities and principles, and since the soul, when elevated with joy and courage, in a manner seeks opposition, and throws itself with alacrity into any scene of thought or action where its courage...

— Hume, David (1711-1776)

Date: 1751, 1777

"They [cruel ideas] still haunt his solitary hours, damp his most aspiring thoughts, and show him, even to himself, in the most contemptible and most odious colours imaginable."

— Hume, David (1711-1776)

Date: 1794

"As those which contribute to circulate the blood, and to perform the various secretions; as well as the associate tribes and trains of ideas, which contribute to furnish the perpetual streams of our dreaming imaginations."

— Darwin, Erasmus (1731-1802)